1. Field of the Invention
The field of the invention is reinforced tapes used with tubing or flexible pipe for conducting petroleum or other fluids subsea or on land and the method of manufacture.
2. Description of the Related Art
This is an improvement on the invention disclosed in U.S. Pat. No. 6,491,779. When the pipe disclosed therein is used to transport compressed gas, some gas can permeate through the inner core or the pipe over time and gather between the inner core and extrusions causing a steady rising inward pressure on the core. Although not in itself a problem under normal circumstances, this can cause a problem if the pressure in the bore of the pipe is released more quickly than the pressure between the layers. When that happens, the inner core can collapse due to the adverse pressure differential and its poor hoop strength. Some degree of protection can be provided to pipes by relieving the pressure between the two extrusions through a valve or valves in the end fittings but this is insufficient for all circumstances and collapse of the inner core may still occur.
Pipe collapse has happened in the past with prior art pipes that have steel based flexible pipes and therefore prior art pipes used for gas transmission are normally constructed using a central interlocking metallic carcass under the inner core. The metallic carcass provides sufficient radial strength to withstand any collapse forces generated by the scenario described above but the overall diameter of the pipe necessarily requires an increase of twice the thickness of the carcass. Furthermore, the inclusion of a carcass increases each reinforcement layer for the same performance because the reinforcement layers have to be wound on larger diameters.